Like I've learned from a chess coach, one only competes to himself, so as long as one does his best and makes progress, one should be happy.
Now, personally, I need to do a better job of learning how to relax, b/c I tend to play way worse in match situations. And then I get upset b/c my level of play has dropped, win or lose.
I think that it take a few years of playing (at least for me) to handle that and build confidence (it has happened in other sports as well).
Some things help, like recently a tip that keeping moving all the time, between hits, helps staying relaxed and also that video about hitting with "minimal effort". Plus the fact that power should come last.